The investigation of the mechanical properties of bone in vivo is of great interest in view of the occurrence of fracture risk in osteopenia or osteoporosis. Osteoporosis may be defined as a metabolic disease causing an unbalance in the natural process of bone resorption and bone formation with the result of a loss of mechanical strength and increased risk of fractures. The degradation of the mechanical strength of the bones may proceed to a stage where even minimal trauma results in bone fractures. Osteoporosis affects more than 20 million people in the U.S. and causes 1.5 million fractures each year. Although age-related bone loss occurs in both men and women, it begins earlier and progresses more rapidly in women. It is estimated that osteoporosis affects about 45 percent of all postmenopausal white women.
An accurate assessment of osteoporosis is difficult. The bones in the skeleton are by nature non-homogeneous and different parts of the skeleton may not be affected to the same degree. The material strength of the bones naturally changes over time, reaching a maximum about the age from 20-30 years and gradually declining later on. Individual differences may be substantial. Treatments do exist which may delay or reverse the progression of osteoporosis. These treatments are most effective when a patient can be diagnosed at an early stage.
The existing technology for predicting fracture risk and osteoporosis often exposes the patient to cumulative doses of X-rays, including, for example, plain X-rays and dual-energy X-ray absorptiometry (DEXA). The risk of long-term effects from X-ray radiation is compounded by multiple exposures whenever the patient is to be reevaluated. Typical X-ray scanners are very expensive and require extensively trained technicians to operate. In addition, the expense and/or inconvenience of existing technology that can only be accessed with an office visit is not conducive to early detection because it limits the number of times a patient will actually be checked. Being tested only every other year or less for the early stages of osteoporosis may not be enough. Studies have shown that in some cases a patient can experience bone loss of up to 10% in a 12 month period. Further, the existing technology may report only bone areal density, and do not directly indicate bone strength or tendency for bone loss, nor do they take into account differences in body build, body weight, patient height, or loading history. In addition, by ignoring bone volume, it is entirely possible that one small vertebra of normal density and another much larger but osteoporotic vertebra will yield the same reading.
Another method of diagnosing osteoporosis is to estimate bone mass through ultrasound velocity measurements. Unfortunately, these tests are limited to bones, such as the calcaneus and patella, which suffer from osteoporosis to a negligible extent and are only weakly indicative of risk of fracture. Traditional bone mass measurements, by their very nature, are unable to predict bone loss prior to its occurrence and can only chart the course of bone loss over an extended period of time. Further, these diagnostics only consider bone mass, and fall to consider bone integrity and other factors such as tendency to fall, or ability to protect oneself during falling. In addition, the capital expense associated with this type of technology can be greater than $7,500.
Because it is desirable to institute treatment for osteoporosis early on, a need exists for an inexpensive, convenient, non-invasive technique for diagnosing fractures and/or osteoporosis in its early stages. The following disclosure may address one or more of these issues.